Full-field quantitative imaging of pore collapse under shock compression

Pore collapse—the rapid closure of pores in materials undergoing dynamic compression—plays an integral role in the shock response of porous materials, and therefore has received much attention within the shock physics community. The local behavior near the pore itself has been extensively studied analytically and computationally, and recent experimental work has revealed the general morphology of the pore as it deforms. However, quantitative experimental results have thus far been restricted to point measurements on the free surface, requiring researchers to infer the local mechanics of pore collapse from free surface velocity measurements and postmortem analysis. In this work, normal plate impact experiments are performed on PMMA and Polycarbonate target plates, with a single spherical pore, at pressures ranging from 0.5-2 GPa. A speckle pattern is applied to the internal plane of the sample, and high-speed imaging (10 million frames/s) is conducted to extract in-plane displacement fields, via digital image correlation (DIC), surrounding the pore as it is subjected to shock compression. These displacement fields are used to compute the full-field strains, which are utilized to quantify the extent of local deformation around the pore, strain concentrations, and localization features which contribute to the previously observed macroscopic behaviors for porous materials.